I. Field of the Invention
The present invention is directed to delivery systems which are suitable for use in the vaginal cavity. Specifically, the invention is concerned with vaginal preparations which demonstrate the controlled-release of active agents for an extended period of time to a site of action or absorption.
II. Description of the Prior Art
One of the main disciplines of medicine is the treatment of the female reproductive system for the prevention, treatment, mitigation, diagnosis and cure of diseases and the prevention of conception. Usually, this involves the delivery of active agents to the vaginal cavity and its environs. Systems to effect the delivery of such agents are usually in the form of gels, foams, creams, suppositories and quick dissolving tablets. These delivery systems, regardless of formulation or method of manufacture, have not demonstrated the ability to deliver active agents in a controlled manner within the vaginal cavity for periods of three hours or longer.
The vaginal cavity is subject to conditions which render it a target for disease and infection; however, it is extremely difficult to deliver an active agent to this area for an extended period of time. The vaginal cavity exhibits an aqueous environment containing secreting glands whose fluids create an acidic pH in the range of 4.5 to 5.5. The environment of the vagina is conducive to the growth of bacteria, fungi, yeast and other microorganisms since it is warm, moist and dark. It is also the vestibule for menstrual debris and the residual seminal fluid from sexual intercourse. The crevices of the vaginal cavity facilitate the retention of undesirable bacteria, fungi, yeast and other microorganisms, as well as the debris from menstruation and sexual intercourse. The vaginal cavity is also subject to considerable physical deformation, such as during sexual intercourse or during the insertion of tampons. Active agents which have pharmaceutical qualities have been developed and approved for use in the treatment of afflictions of the vaginal cavity and the prevention of conception. These include fungicides, spermicides, etc. Although pharmaceutically active agents have been developed, it has been difficult to achieve optimal potential effectiveness from these agents due to the inadequacy of currently available delivery systems. No system which is approved or even suitable for use in the vaginal cavity has been shown to release a pharmaceutically active agent for periods of three hours or longer. This also is true of aesthetically oriented systems, such as acidifiers and deodorants. The gels, foams, creams, suppositories and tablets that are presently used as vaginal delivery systems breakdown almost immediately following insertion into the vaginal cavity and have minimal bioadherence to the vaginal walls. This is believed due to their water miscibility and/or their lack of physical stability at 37.degree. C. (body temperature). Thus, they exhibit limited effectiveness since they rapidly release their active agents in an uncontrolled manner. Conventional dosage forms are frequently discharged as an offensive leakage and drippage along with the minute vaginal secretions that are a normal physiological function.
The present invention is advantageous in that it provides a system for the delivery of an active agent in a controlled manner in the vaginal cavity for an extended period of at least three hours. The system may take the form of a multi-phase liquid or semi-solid which is easily introduced into the vaginal cavity but does not seep from this body cavity in an offensive manner.